WASHINGTON — The Justice Department will not bring criminal charges against former Ferguson, Mo., police officer Darren Wilson, whose fatal shooting of a black teenager prompted waves of protests and a national re-examination of law enforcement's relationship with minority communities.

The decision, outlined in an 86-page memorandum made public Wednesday, states that the officer, who is white, acted in apparent self-defense.

The conclusion of the shooting investigation, along with the Justice Department's separate scathing denouncement of racially biased policing operations in Ferguson, comes six months after Michael Brown, 18, was shot by Wilson, setting off demonstrations that spread across the country.

Attorney General Eric Holder characterized the outcome of the shooting investigation as representing the "sound, considered and independent judgment of the expert career prosecutors within the Department of Justice.''

"I concur with the investigative team's judgment and the determination about our inability to meet the required federal standard'' of proof, Holder said.

In the shooting inquiry, federal investigators said, "Several witnesses stated that Brown appeared to pose a physical threat to Wilson'' on Aug. 9 when Wilson stopped the teenager, a suspect in a convenience store theft, for walking in the street.

"According to these witnesses, who are corroborated by blood evidence in the roadway," the inquiry states, "Wilson fired at Brown in what appeared to be self-defense and stopped firing once Brown fell to the ground.

"There is no evidence upon which prosecutors can rely to disprove Wilson's stated subjective belief that he feared for his safety,'' the report concludes.

Investigators focused closely on the actions of both Wilson and Brown during an encounter that lasted just two minutes on that hot early afternoon. During those moments, Brown argued with the officer while Wilson sat in his patrol vehicle, then reached into the open window in an apparent struggle for control of the officer's gun. Wilson filed the weapon during the struggle, striking Brown in the right hand.

After the initial gunfire, investigators said, Brown fled, and Wilson chased him on foot. About 180 feet into the chase, Brown turned around and "came back toward Wilson."

Although several witnesses have asserted that Brown raised his hands in a sign of surrender before the fatal shots were fired, "some of those accounts are inaccurate because they are inconsistent with the physical and forensic evidence," the report found.

Parents of Michael Brown, Lesley McSpadden, left, and Michael Brown Sr., lead a rally in Ferguson, Mo., on Aug. 30, 2014, near the site where Michael, an unarmed black 18-year-old, was fatally shot by a white police officer three weeks earlier.(Photo: Bill Boyce, AP)

Justice officials met with Brown's family earlier Wednesday to inform them of the decision not to prosecute Wilson.

"Today, we received disappointing news from the Department of Justice that the killer of our son wouldn't be held accountable for his actions," Brown's parents said in a written statement. "While we are saddened by this decision, we are encouraged that the DOJ will hold the Ferguson Police Department accountable for the pattern of racial bias and profiling they found in their handling of interactions with people of color.

"It is our hope that through this action, true change will come not only in Ferguson but around the country. If that change happens, our son's death will not have been in vain."

Wilson's attorneys could not be reached for comment Wednesday. St. Louis County Police Association spokesman Jeff Roorda, whose organization has strongly supported Wilson since the shooting, said the government's conclusion is "the right decision."

"The evidence points to it,'' said Roorda, the association's business manager. "I am sure it is a relief to (Wilson) and his family. He deserves to move on with his life."

Officials had signaled weeks before the release of Wednesday's report that a prosecution was not likely. But its separate examination of overall police operations found rampant evidence of racial bias in a department that had long ago lost the public trust of its African-American residents, who represent 67% of the city's population.

Among the most serious findings in the review: In nearly 90% of cases in which Ferguson documented the use of force, those actions were used against African Americans. A review of 161 such cases by Justice investigators found that none of the incidents resulted in disciplinary action.

The inquiry also discovered a trove of what Holder described as "grotesque" racially charged e-mails written by members of the police department and other city agencies. Some mocked President Obama, one of which depicted the nation's first black president as a chimpanzee.

Some of the e-mails, investigators concluded, had been circulated to top city leaders, including the city manager. Yet the Justice inquiry found that no officer or city employee "engaged in these communications was ever disciplined.''

"Nor did we see a single instance in which a police or court recipient of such an e-mail ask that the sender refrain from sending such e-mails,'' the report found. "Instead, the e-mails were usually forwarded along to others.''

Justice officials recommended that the city institute more than two dozen policy actions. The recommendations call for increased officer supervision, more civilian oversight of department operations, a system for tracking ticketing that disproportionately targeted African Americans and the creation of a disciplinary system to address misconduct.

Federal authorities are seeking a formal agreement with the city that would begin a process of installing the recommended changes. If no such agreement can be reached, Justice authorities said they could seek a court order to force the action.

Ferguson Mayor James Knowles said in a brief statement late Wednesday that the city had cooperated fully with the Justice investigation. Addressing the findings related to racially-charged emails, Knowles said three employees were responsible for all of the missives, one of whom has been fired and two others are on administrative leave pending the completion of an internal investigation.

"We must do better, not only as a city but as a state and a country," Knowles said. The mayor said the city is planning to bring civilian oversight to its policing operations and was engaged in hiring a more diverse workforce, along with restructuring its municipal court operations so that poor residents would not be saddled with excessive and unnecessary fees.

Knowles, however, did not address problems with how police used physical force against its largely African-American residents and it routinely targeted blacks for traffic stops and arrests.

In a separate statement, Missouri Gov. Jay Nixon described the Justice findings as "deeply disturbing,'' demonstrating an urgent need for reform.

"Discrimination has no place in our justice system and no place in a democratic society,'' Nixon said. "All Missourians deserve to be treated with fairness, dignity and respect.''

The Justice findings also drew strong reaction among area residents, some of whom said the report affirmed their own experiences.

Nathan Burns, 25, who lives four blocks away from Ferguson in an unincorporated city in St. Louis County, said racial bias stretches far past Ferguson and policing. He said racism impacts the lives of blacks in schools, at jobs and in everyday interactions.

The high school algebra teacher hopes the report will make people reflect on the experiences of discrimination in other aspects of black life. Burns said he has been pulled over more than 20 times by officers working for various St. Louis-area departments in the past eight years. At times, Burns said, officers searched his car and home for no reason while he and friends sat on their front porches. Burns said he and many of his friends who are black have been targeted because of their race.

"There's a culture that has been created," Burns said. "A lot of people want to say racism is over with and that we are past that. But time doesn't make everything disappear. Ignoring the fact that you have cancer is not going to stop you from having cancer. And racism is like a cancer that people have been ignoring."

Ferguson real estate company owner Marion Blocker, 26, said he gets pulled over by various police departments about three times a month while driving his 2004 black Monte Carlo. He said the government's conclusions reminded him that African Americans need to be mentally prepared to remain cool during interactions with officers.

"Our reaction is everything," he said. "We need to know our rights and know how to be able to protect ourselves even if we know this is what's against us."

Blocker has learned what constitutes an illegal search as well as how to properly communicate his feelings to police if he believes an officer isn't applying the law correctly. He hopes other African Americans do the same and teach their children.

"Racism is being taught every day," he said. "It's so ingrained in just the human existence of who we are. ... I fit the description, but who doesn't fit the description of being black and driving?"